So, hypothetically, if I live with a vampire, how much blood can I offer?

For example, if I was to let them suck my blood every Sunday, would that be okay for my health? How fast does the blood replenish? How much is too much before I die?

Before you ask, no, chicken blood and such doesn't seem to work as substitution. Also, once a week is the bare minimum before they go kinda crazy with random people, and then it's hard to cover up